What is CVE-2023-33009?

CVE-2023-33009 is a critical-severity vulnerability in Zyxel Atp Series Firmware, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2023-05-24.

How severe is CVE-2023-33009?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2023-33009 known to be exploited?

Yes. CVE-2023-33009 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-06-05), indicating it is being actively exploited. 3 public proof-of-concept repositories are indexed.

Buffer overflow in Zyxel Atp Series Firmware

CVE-2023-33009

A buffer overflow vulnerability in the notification function in Zyxel ATP series firmware versions 4.60 through 5.36 Patch 1, USG FLEX series firmware versions 4.60 through 5.36 Patch 1, USG FLEX 50(W) firmware versions 4.60 through 5.36 P…

Vulnerability class: Buffer Overflow

EPSS: 0.056 (90.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Zyxel Atp Series Firmware — versions 4.60 through 5.36 Patch 1
Zyxel Usg20(w)-vpn Firmware — versions 4.60 through 5.36 Patch 1
Zyxel Usg Flex 50(w) Firmware — versions 4.60 through 5.36 Patch 1
Zyxel Usg Flex Series Firmware — versions 4.60 through 5.36 Patch 1
Zyxel Vpn Series Firmware — versions 4.60 through 5.36 Patch 1
Zyxel Zywall/usg Series Firmware — versions 4.60 through 4.73 Patch 1

Weakness classification (CWE)

CWE-120 — Buffer Copy without Checking Size of Input (Classic Buffer Overflow)

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2023-06-05. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2023-06-26.

Required action: Apply updates per vendor instructions.

Public proof-of-concept exploits

References

www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for…

Frequently asked questions

What is CVE-2023-33009?: CVE-2023-33009 is a critical-severity vulnerability in Zyxel Atp Series Firmware, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 9.8/10. Published 2023-05-24.
How severe is CVE-2023-33009?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2023-33009 known to be exploited?: Yes. CVE-2023-33009 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2023-06-05), indicating it is being actively exploited. 3 public proof-of-concept repositories are indexed.